An optimization of microtube heat exchangers for supercritical CO₂ cooling based on numerical and theoretical analysis

This paper presents a new simulation method with lower computation consumption for microtube heat exchangers (MSTEs) used for supercritical CO₂ cooling, which maintains high precision. The heat transfer characteristics in the shell pass and tube pass and the relationship between them are both analyzed. Baffles lead to various regions with different follow patterns and heat transfer features in the shell pass. Furthermore, higher heat transfer performance in the shell pass leads to heat transfer enhancement in the tube pass due to the CO₂ near-pseudocritical characteristics. The optimization method based on the eigenfunction of ΔP_i = F(A_i) which characterizes the influence of baffles on the comprehensive performance of MSTEs focuses on the difference among local heat exchange and pressure loss in multiple segments and guides to reduce the pressure loss while the heat transfer load and area remain unchanged. The optimized baffles arrangement is found according to the numerical results and the optimization method. The comparison between the simulation results of the original and optimized MSTEs shows that the optimization method is effective for heat exchangers with variable local heat exchange features and pressure loss performances.